This is a proposal from the Department of Biological Sciences, Oakland University (Rochester, MI) for funds to purchase a MT6000XL ultramicrotome. At present, the department has two Sorvall MT2B ultramicrotomes which were purchased more than fifteen years ago. In the last ten years, the number of faculty members and their staff using these ultramicrotomes and electron microscope facilities has more than doubled. Moreover, the age of these existing microtomes and unavailability of some of the parts has resulted in a considerable amount of "down'' time and high cost of maintenance. These problems have resulted in slow progress made by investigators in their research, some of which is supported by the National Institutes of Health. The department is in acute need of a "state-of-the-art" ultramicrotome to enable investigators to efficiently continue transmission electron microscope related studies of biological materials. The decision to request funding for MT6000XL ultramicrotome was made for several reasons: 1) it is a state-of-the-art ultramicrotome with a proven record for the preparation of ultrathin sections for microscopy, 2) it is easy to operate, 3) it is possible to increase its capacity in future years to obtain cryosections, 4) familiarity of users with similar instruments, 5) it is manufactured in the United States, and 6) service is readily available.